1. Field of the Invention
The present invention relates generally to specimen inspection and review. More particularly, the present invention relates to electron beam inspection and review systems.
2. Description of the Background Art
Automated inspection and review systems are important in process control and yield management for the semiconductor and related microelectronics industries. Such systems include electron beam (e-beam) based systems.
FIG. 1 is a simplified schematic representation of a conventional electron column and collection system for electron beam inspection. In brief, FIG. 1 shows a schematic diagram of the various electron beam paths within the column. Electrons are emitted radially from field emission cathode 81 and appear to originate from a very small bright point source. Under the combined action of the accelerating field and condenser lens magnetic field, the beam is collimated into a parallel beam. Gun anode aperture 87 masks off electrons emitted at unusable angles, while the remaining beam continues on to beam limiting aperture 99. An upper deflector (not depicted) is used for stigmation and alignment, ensuring that the final beam is round and that it passes through the objective lens (not depicted). A condenser lens (not depicted) is mechanically centered to the axis defined by cathode 81 and beam limiting aperture 99. The deflection follows the path shown, so that the scanned, focused probe emerges from the objective lens to impact on the substrate 57.
As a result of the impact of the primary beam onto the substrate 57, scattered electrons are generated. The scattered electrons may include secondary electrons and backscattered electrons. Wien filter deflectors 112 deflect the scattered electron beam 120 into the electron detector 117.